Poor reading comprehension (RC) has significant public health consequences. About 25-30% of adolescents in the U.S. perform at a Below Basic level, a level that does not promote successful academic achievement; however, successful RC intervention for much of this population has been elusive. The evidence suggests that there are multiple factors contributing to RC failure, but we do not yet have a clear understanding how these factors interact over development to affect RC. First, there is scant neurobiological understanding of listening comprehension and word recognition development (the so called Simple View of RC) as related to RC, even though we have shown neurobiologically the importance of speech and print binding for predicting individual differences in reading. Second, research by us and others increasingly shows that executive function (EF) is related to RC, mostly in older readers, thus providing initial neurobiological links to RC theories that include higher order reasoning (Construction-Integration). Despite these findings, it is currently unknown how the neurocognitive correlates of EF influence RC development. The next 5 years of HD044073 thus proposes to fill these gaps in the literature by using a longitudinal design that follows children from 2nd-5th grades, first probing the foundational question of how the neurobiological correlates of word and comprehension-level processing development, across modalities, predicts 4th/5th grade RC outcome (Aim 1). Then, we focus on the role that EF plays across RC development (Aim 2). Such knowledge may reveal the importance and role of EF in the transition from learning-to-read (word recognition emphasis) to reading-to-learn (RC emphasis). Our multimodal neuroimaging and behavioral measures together enable a unique window into neurocognitive systems across RC development, and have the potential for moving forward RC theoretical models and providing insights into why some continue (or sometimes begin) to struggle to read as they get older. In particular, using neuroimaging to capture changes in language networks, thus mapping of the Simple View into measurable patterns of integration and changing connectivity in the brain, will allow us to move toward causal brain based accounts of the powerful but poorly understood link between spoken and written language. Understanding how these skills integrate neurobiologically over RC development (and the role of EF in guiding integration) may hold some answers about targets for early intervention and prevention, especially for older poor readers who typically have both lower and higher-level deficits. Ultimately, this line of work may guide the development of more tailored treatments at more optimal time points, and provide a clearer understanding of how to identify and treat RC deficits (or risk factors/precursors thereof) prior to 4th grade. In summary, we seek to provide a fine grained study of the neurobiological correlates of RC development to understand more about how the transition between critical reading stages happens. The overarching long range goal is to treat RC failure before it impedes school learning. Such work could have wide-ranging implications and public health importance.